1. Field of the Invention
The invention relates to a device for visually inspecting the condition of large-dimension surfaces to be matched, especially painted bodywork, with substantially vertical and horizontal surfaces to be matched.
2. Description of the Prior Art
From prior art, optical devices for assessing the color of small surfaces are known; however these devices cannot be used for assessing large surfaces, for example whole vehicle bodies in automobile manufacture. Furthermore, different illumination structures for recognizing surface faults are known, with which the person involved has to look directly into the lamp and is thus dazzled. Moreover, the known arrangements for recognizing surface faults cause shadows to be cast by the people working, whereby fault recognition is only possible at certain positions which differ greatly from one another. The known devices for recognising surface faults do not permit simultaneous recognition of colour faults.
The purpose underlying the invention therefore is a device for visually inspecting the surface condition of large-dimension surfaces to be matched, by means of which device it is possible to recognize both surface faults and colour faults on large-dimension areas, especially painted bodywork, the workers not being dazzled and no shadow being cast by the workers.
This purpose is fulfilled according to the invention by the characteristic features of the main claim.
The visual inspection of surfaces to be matched includes both the matching of color, color effects and gloss and the recognition of paint faults. The recognition of the different faults requires respectively specific relationships between the observation direction and the illumination direction, and the design of the environment is also of great importance. For color matching, for example, oblique incident light radiation connected with vertical observation is favorable, a low luminance of the space delimitation reflected on the glossy surface to be matched being important, since too sharply defined overlaid illumination structure or luminance of the space delimitation is imposed on the impression of color and the recognition of color differences is hindered. This means that the lights or lamps may not reflect on the surfaces to be matched.
On the other hand, for the recognition of surface faults, reflection of the lighting structure is advantageous since faults at the corresponding reflected light/dark boundaries become visible through an alteration of the course.
For the invention, the following relationships arise between beam paths and types of fault or visual tasks:
Beam paths with reflected illumination structure permit the recognition of surfaces which are marked by geometrical deformation of the observed surface. Moreover the assessment of gloss and the assessment of the effect of effects paints is made possible. PA1 Beam paths without reflection of the illumination structure make possible the recognition and the comparison of colors as well as the recognition of surface faults which do not result in any geometrical deformation of the surface. Through alteration of the illumination and/or observation angles, likewise color effects become visible. PA1 Small glancing angles, for example approximately 15.degree., cause beam paths on which the illumination structure is reflected so that surface recognition is possible. PA1 Large glancing angles, for example approximately 45.degree., prevent the reflection of an illumination structure, which is useful in color matching.
To distinguish the various beam paths, the glancing angle must be taken into account, this glancing angle being defined as the angle by which the angle of observation deviates on a directed reflection from the direction of the reflected light ray. According to the size of the glancing angle, two observation geometries thus arise:
Taking into account the above realizations, the purpose underlying the invention is fulfilled in that a plurality of luminous elements are provided in a fixed relationship to the surface to be matched, whose principal radiation direction, with a vertical arrangement and viewed in horizontal planes, is directed at oblique angles to the surfaces to be matched, the luminous elements being provided with screening devices, which are effective in a direction between the principal radiation direction and the direction perpendicular towards the surface to be matched, in such a way that, at least in observation of the measurement from the angles close to the direction of the normals, no luminous parts of the luminous elements are reflected on same. The luminous elements are here so screened, that rays, which hit the luminous elements from directions of the normals of the surface to be matched and in an angle range around the normal, either directly or after reflection on the light-deflecting reflectors allocated to the luminous elements, hit light-absorbent screens.
Through the device according to the invention in which the luminous elements radiate at an oblique angle, preferably below 45.degree., onto the surfaces to be matched, both surface faults of every kind and color faults as well as further surface effects for example the sag in metallic paints, may be recognized, the observer, when matching the object, being located between said object and the luminous elements, and through changing his location and/or through changing the direction of observation, all the required beam paths and observation paths can be realized. The luminous elements are protected against being looked at directly from the direction of the normals of the surfaces to be matched and in an angle range around the normal against being looked at directly, and thus remain without light radiation in these directions. Dazzling of the observer and the overlaying of the observation field by illumination reflexes in the case of color inspection do not occur.
Through the measures quoted in the subordinate claims, advantageous developments and improvements are possible.
The surfaces to be matched can be disposed horizontally vertically but also at an angle. Under the term `substantially vertical and horizontal surfaces to be matched` as they occur on painted bodywork, those surfaces should also be understood which are slightly curved, a corresponding adaptation of the illumination geometry being possible, if desired.
The quality of the matching of horizontal surfaces, for example roof surfaces on vehicle bodies, can be improved by ceiling illumination, which preferably radiates the light at an angle, and is screened advantageously from directions perpendicularly from below and in an angle range around this direction. The observation of the vertical surfaces, for example the side surfaces of the vehicle bodies, can in the region close to the floor be improved by floor lights shining upwards, especially in an alignment transversely to the surface to be observed. The floor and ceiling luminous elements can be replaced by mirrors on the floor or ceiling to continue the illumination geometry of the side walls.
In the simplest case, according to the invention, the light distribution and shading of the illumination arrangement can be realised by a luminous wall or a plurality of individual lights, possibly already with bundled light distribution, of which perpendicular lamellae, aligned substantially parallel to the desired principal radiation direction, are disposed so closely beside one another that looking directly in an angle region around the normal of the perpendicular surface to be matched is no longer possible.
Through configuration of the luminous elements as lights with a reflector which preferably has a uniaxial curvature, and which bundles the light of one or more elongate lamps disposed parallel to the reflector axis, preferably fluorescent lamps, in planes transversely to the lamp axis, a disc-shaped screen being disposed preferably parallel to the principal radiation direction running towards the lamp, an illumination device is made available with lights which have integrated dazzle-reduction devices and are of flat construction with high lamp efficiency. Moreover these lights can be inserted as individual modules.
Moreover the shielding can be improved in that a plurality of screens is arranged in the one reflector half parallel to the first screen.
Color matching is improved and made more variable in that at least the screen surfaces which face the reflector portion and on which the incident light rays reflect, are absorbent and neutral in color, for example black or grey, which results in a sufficient reduction in luminance to avoid dazzling and irritations during the matching.
A further reduction in the constructional depth of the lights results from the fact that the one reflector half, which is turned towards the observer, is cut away, the central screen then being able to represent the housing wall of the reflector. Furthermore it is advantageous to provide a light-collecting reflector around the lamp. This light-collecting reflector can here either send the light back into the lamp with the effect of a small basic dispersion of the system, but with lower efficiency, or can go round the lamp with the effect of a larger basic dispersion and higher efficiency. In an advantageous development, the lights may be dimmed, a decline in the luminous flux of the lamps in the course of their service life being compensated for by the lamps being operated in the dimmed state and the dimming being withdrawn with an increasing drop in the luminous flux. Moreover, being dimmable has the advantage that, through a plurality of matching lights, a desired luminous intensity profile can be set on a surface to be inspected.
In advantageous manner, in order to reduce absorption losses on the outer surfaces to a minimum, reflective external reflectors which are directed to the lateral outer surfaces of the lighting housing may be attached and preferably be embodied as a continuation of the reflector of the light disposed beside it, the reflectors being able to be integrated at least partially into the housing shape.
On the other hand, however, these surfaces can also be realized in a neutral color with a low degree of reflection, in order to avoid reflexes.